The Role of Serum Procalcitonin in Predicting Bacterial Sepsis in Patients With Hypothyroidism.

CONTEXT: Serum levels of procalcitonin (PCT), a protein produced by the thyroid C cells under physiologic conditions, are high during sepsis. OBJECTIVE: To assess the test performance of serum PCT in predicting bacterial sepsis and septic shock in patients with hypothyroidism compared with those who have euthyroidism. DESIGN AND METHODS: This retrospective study evaluated patients with no history of thyroid dysfunction (euthyroid), primary hypothyroidism [medical hypothyroidism (MH)], and postsurgical hypothyroidism from total thyroidectomy (TT) identified from a prospectively maintained database who had PCT testing from 2005 to 2018. Quick Sequential Organ Failure Assessment score ≥ 2 or positive bacterial cultures identified bacterial sepsis, and a mean arterial pressure less than 65 mm Hg or a vasopressor requirement defined septic shock. Sensitivity and specificity of PCT for evaluation of bacterial sepsis and septic shock were measured. RESULTS: We identified 217 euthyroid patients, 197 patients with MH, and 84 patients with TT. Bacterial sepsis was found in 98 (45.2%), 92 (46.7%), and 36 (42.9%) of these patients, respectively (P > 0.05). Septic shock was identified in 13 (6.0%), 13 (6.6%), and 5 (6.0%) patients (P > 0.05), respectively. With use of a PCT cutoff of 0.5 µg/L for bacterial sepsis, the sensitivity was 59%, 61%, and 53% (P > 0.05) and specificity was 81%, 77%, and 81% (P > 0.05) for the diagnosis of bacterial sepsis in euthyroid, MH, and TT patients, respectively. With use of a PCT cutoff of 2.0 µg/L for septic shock, the sensitivity was 46%, 62%, and 63% (P > 0.05) and specificity was 86%, 82%, and 91% (P > 0.05) for the diagnosis of septic shock in these patients, respectively. CONCLUSIONS: Despite the thyroidal origin of PCT, hypothyroidism did not affect the diagnostic performance of serum PCT levels in predicting bacterial sepsis or septic shock.